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Interactions of Tollmien-Schlichting Waves and Stationary Transient Disturbances

Gurun, Akif Murat
http://rave.ohiolink.edu/etdc/view?acc_num=case1133374397

Abstract Details

2006, Doctor of Philosophy, Case Western Reserve University, Mechanical Engineering.
Numerical simulations have shown that stationary, spanwise periodic transient disturbances are capable of suppressing the growth of Tollmien-Schlichting (TS) waves in boundary layers. A natural implication is that the deliberate introduction of transient disturbances may delay TS-dominated transition. This experimental study investigates the interactions of these two types of disturbances and the breakdown of TS waves with and without transient disturbances. TS waves are created using a combination of acoustic forcing and a two-dimensional roughness strip while transient disturbances are created using a spanwise array of cylindrical roughness elements. It is found that in the presence of stationary transient disturbances, wall-normal velocity profiles of the unsteady TS-like waves are modulated and their growth rate is reduced. The modulated wall-normal velocity profiles have a characteristic M-shaped appearance and this shape appears to be mainly due to the component of the unsteady disturbances that varies on the spanwise wavelength of the stationary disturbances and higher spanwise harmonics of this wavelength. An important finding with respect to transition control applications is that the receptivity of the TS waves is reduced when the spanwise roughness array is present. The underlying mechanism responsible for this reduction is not yet known. Additionally, it has been found that unsteady disturbance amplitudes at breakdown are reduced when transient disturbances are introduced and, therefore, the breakdown location is actually moved upstream when care is taken to match initial unsteady disturbance amplitudes. It is concluded that even though TS growth is reduced, transition to turbulence is not successfully delayed.
Edward White (Advisor)
114 p.
Transition; Boundary Layers; Tollmien-Schlicting Waves; Transient Growth; Turbulence; Secondary Instability; Wind Tunnel; Transition Delay; Data Acquisition

Recommended Citations

Citations

  • Gurun, A. M. (2006). Interactions of Tollmien-Schlichting Waves and Stationary Transient Disturbances [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1133374397

    APA Style (7th edition)

  • Gurun, Akif. Interactions of Tollmien-Schlichting Waves and Stationary Transient Disturbances. 2006. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1133374397.

    MLA Style (8th edition)

  • Gurun, Akif. "Interactions of Tollmien-Schlichting Waves and Stationary Transient Disturbances." Doctoral dissertation, Case Western Reserve University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=case1133374397

    Chicago Manual of Style (17th edition)

case1133374397
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© 2005, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.